Is there more than one size square radiater key?

i have a customer with a 20 yr old hot water boiler,,360k btu....house is much older with very old radiaters...had a circulater problem that caused major water leak from boiler system...problem is fixed but my standard size radiater key is too large for the square shaft that is inside the bleeder fittings...no one seems to have heard of this except one explanation i got was that possibly the radiaters may have had knobs that were attached to these small square shafts..the knobs eventually broke off,leaving these odd size shafts that there is no key for???...do they make 4-point sockets, one of which might fit...or does a plumber need to replace the entire bleeder port on the radiaters that have this issue?................dan